References:
1. Redlich, R., and Davidson, T., "An Integral Monitor for the ILS Localizer". IEEE Transactions on Aerospace and Electronic Systems. Sept., 1966, pg. 618. PA1 2. Petersen, C., "Localizer Traveling Wave Antenna Development". Department of Transportation, Federal Aviation Administration. Report No. FAA-RD-76-129. May, 1976, pgs. 10,22,23. PA1 (a) divide each V(n) into three channels PA1 (b) introduce phase lags in each channel according to equation (1) PA1 (c) sum the phase shifted signals in each channel.
Instrument Landing System (ILS) Localizer signals must be continuously monitored to ensure that aircraft executing an ILS approach receive safe and accurate guidance. Monitoring requires ground based prediction of the signals radiated by the localizer array. Antennas in the near field of the Localizer transmitting array have been used to obtain monitoring signals, but these produce inaccurate predictions of far-field performance.
So called "Integral monitors" are in wide use and generate analogs of the far-field radiated signal at one or more angles from runway centerline. Such monitors according to current practice generate analogs of far-field signal on runway centerline ("course" signal) and of far-field signal at an angle of about two degrees from runway centerline ("width" signal). Monitoring of a third angle in the so called "clearance" region from twenty to thirty five degrees from runway centerline is frequently necessary. Integral monitors in current use which monitor a clearance angle do not generate a true far field analog because of the nearly twofold increase in components which would be necessary to analog monitor a third angle, and because of difficulties in monitoring a relatively large angle using current analog technique. Consequently the clearance signal produced by currently used monitors may not correlate with far-field measurements.
The present invention remedies the deficiencies of presently used integral monitors by generating accurate analogs of far field signals on course, at the width angle, and at an angle in the clearance region. Further, the invention uses inexpensive, compact, and reliable components.